Naysayers underestimated Disney World this time. Granted, when the company announced plans in September to project photographs of theme-park guests onto Cinderella Castle at Magic Kingdom, details were sparse.

But who, beyond Imagineers, could have dreamed of the jam-packed, special-effects Disney spectacle that is now known as"The Magic, the Memories and You"?

"It's a heck of a lot more than a slide show on the castle," said show director Alan Bruun before the show was shown to media members last week. It officially debuted last Wednesday, and it will continue through 2011.

The show is tagged to the promotional campaign, "Let the Memories Begin," and it features same-day photos of guests taken by Disney photographers. Each showing requires 500 fresh snapshots.

Those smiling, personal pictures may be special to those who appear on the castle canvas, but to the vast majority of viewers, the special effects are the stars of the show.

During the course of "The Magic, the Memories and You," Cinderella Castle appears to undergo radical changes: Vines grow up the sides, giant bubbles float by, doves escape through the opening and the normally solid structure presents a ripple effect.

The opening minutes are accompanied by a soaring new, Broadway style anthem called, unsurprisingly, "Let the Memories Begin." Its musical hook is heard repeatedly — once sung by an animated cow — during the ensuing Disney ditties, which include"Be Our Guest," "It's a Small World," "Supercalifragilisticexpialidocious," "Bear Necessities" and"When You Wish Upon a Star."

There's a bit of mash-up in the songs (See "Glee"), but the show also mixes elements from the Disney catalog. When Julie Andrews, as Mary Poppins, says "with every job that must be done, there is an element of fun," the soundtrack becomes"Whistle While You Work." After Buzz Lightyear says "to infinity and beyond," the music shifts to "A Whole New World" from"Aladdin" and the castle morphs into one of its best effects: The tallest turret becomes a rocket that blasts off.

The iconic castle has more tricks, thanks to 16 high-powered projectors placed around the park.

A "Pirates of the Caribbean" segment makes the castle look aflame. Later, there are dancing skeletons, a tower-turned-train whistle, sudden color changes, flying bricks, Mickey Mouseaboard Dumbo, and the castle re-imagined as "it's a small world."I didn't see a kitchen sink, but I wouldn't be surprised.

Bruun, the show director, says Disney's photographers have been instructed on what looks work best in the show.

"All of those moments that are truly authentic as opposed to the standard posed shots," he says. A number of themes run through the show, Bruun says, and the photos need to reflect tones such as happiness and adventure. Screeners pick the best of those categories, and then technology takes over.

"There are a couple of places where there are very, very specific shots that we're looking for … and the computer picks those out because those have been highlighted in a particular way," Bruun says.

Guests can opt out of being used in the show, but honestly, the odds are long. And the odds of actually catching your image up on the castle walls are even longer. They are only seen for seconds, and if you're standing on one side of the structure, it could be shown in your blind spot on the other side. Or maybe you'll be distracted by the effects.

The biggest photos are saved for the end, when a shot can take up the top half of the castle. This is building to a video finale with Walt Disney welcoming all to the park.

The show — at 9 minutes, 45 seconds — ends with a pinch of pyrotechnics, but it's just a warm-up for the "Wishes" fireworks that will remain part of the nightly lineup.

On 200 nights, there will be two rounds of "The Magic, the Memories and You."

"When we do that, we'll repopulate the show with 500 new images, so on those days we're looking for over 1,000 images," Bruun says.

So, smile, everybody.